How to read custom dimension attribute from java code

Issue

I made my custom component just putting few TextViews together. Now I want to be able to init my custom control directly from code, passing text sizes independently for each of of TV's

My attributes definition:

<resources>
    <declare-styleable name="BasicGauge">
        <attr name="valueTextSize" format="dimension" />
        <attr name="titleTextSize" format="dimension" />
        <attr name="unitsTextSize" format="dimension" />
    </declare-styleable>
</resources>

Sample initialization of component:

<pl.com.digita.BikeComputerUi.customviews.BasicGauge
    android:id="@+id/basicGauge1"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:padding="10dp"
    valueTextSize="40sp">

</pl.com.digita.BikeComputerUi.customviews.BasicGauge>

How I try to read those attributes in component's constructor:

final int N = typedArray.getIndexCount();
for (int i = 0; i < N; i++) {
    int attribute = typedArray.getIndex(i);
    switch (attribute) {
        case R.styleable.BasicGauge_valueTextSize:
            valueTextSize = typedArray.getString(attribute);
            break;
        case R.styleable.BasicGauge_titleTextSize:
            titleTextSize = typedArray.getString(attribute);
            break;
        case R.styleable.BasicGauge_unitsTextSize:
            unitsTextSize = typedArray.getString(attribute);
            break;
    }
    typedArray.recycle();
}

Problem: After creation all of my values are still null. 40sp is exactly my desired value.

Solution

A few things to say :

• first you need a xml name space declaration line at the top of your xml, exactly in the same way as you do with android xmlns : xmlns:foo="http://schemas.android.com/apk/res-auto"
• then you need to prefix valueTextSize with your xmlns : foo:valueTextSize="40sp"

After that, it's not a very good idea to get a string, android offers more powerfull solution to deal with dimensions :

int unitsTextSize = typedArray.getDimensionPixelSize(R.styleable.BasicGauge_unitsTextSize, textSize);

then there are some subtleties :

• for a Paint, or a TextPaint, you can this value as is : paint.setTextSize(unitTextSize):
• for a textview, the above approach would fail, and you have to use an overload of setText to get the correct result : textView.setTextSize(TypedValue.COMPLEX_UNIT_PX, unitTextSize);

The difference comes from what is called "raw pixels" (unscaled according to density, just raw) and "scaled pixels" (the opposite).

Answered By - Snicolas